Mechanical braking system



Dec. 11, 1956 E. D. GARRETT MECHANICAL BRAKING SYSTEM 7 Filed Aug. 11, 1950 INVENTOR. frnes 7 D. Ga/v-e ff United States Patent MECHANICAL BRAKING SYSTEM Ernest D. Garrett, Shreveport, La., assignor of one-half to David G. Crow, Shreveport, La.

Application August 11, 1950, Serial No. 178,904

7 Claims. (Cl. 188-77) My invention relates to mechanical braking systems generally, but more in particular to a mechanical braking system for use on heavy hoisting equipment such as might be found on the draw works of an oil well drilling rig.

In prior inventions of the present type, considerable efiort has been put forth to produce a compact braking system for a drilling rig which would not only insure perfect control of the cable drum, but also be mechanically safe without attention or repair for considerable periods of time.

It is well known to those familiar with this type machinery, and more in particular the braking systems installed in oil well rigs, that the brakes must at all times be capable of stopping heavy loads suddenly and also making possible a payout of the line without jumping or seizing while the load is being handled. Since the brakes must support several thousand feet of pipe and cable, it is readily apparent that extreme care should be given to the design of the braking system so that the operator may stop the lowering or raising of the pipe string at a moments notice or signal and that within a minimum variation from a given stopping position. For example, when a joint of pipe is added to the upper end of a pipe string being lowered into the well hole, the driller must lower the string so that the upper threaded end is within reach of the workmen on the derrick floor for the addition of another joint. From constant practice and experience, the driller is able to lower the string in a matter of seconds and stop the upper threaded joint within a few inches of the same spot each time a joint is added. Should the brakes fail, it can be easily seen that not only will the entire string be dropped into the well hole, but the loose cable will endanger both men and equipment on the derrick floor.

When drilling, the entire pipe string is supported by the draw works of the rig and the weight of the pipe string is allowed to force the bottom bit into the earth. This lowering of the string must be slow and smooth so that the bit will not tend to dig into the formation or be wedged in rock and become damaged. In faulty brakes which usually allow a jerky movement when under a heavy load which is released slowly, it is apparent that a lower drilling bit is likely to become damaged.

Most of the mechanical braking systems arranged for use in drilling rigs consist of a pair of brake shoes partially encircling the outer ends of the cable drum and supplied with some leverage system finally connected to the main operating lever by-which the brakes are applied. The arrangement of this leverage system as disclosed by the prior art has permitted the use of only 60 to 75 percent of the braking surface which has resulted in ineflicient utilization of the braking drums, hence considerable wear on the brake shoes; The prior art does not disclose a system whereby the brakes are easily equalized when applied and released, nor does it show any arrangement by which one brake may be used to stop the drum rotation should a failure occur in the other,

Patented Dec. 11, 1956 It is apparent that these features incorporated into a braking system would be highly advantageous when applied to an oil field drilling rig.

It is an object, therefore, of the present invention to provide a braking system for an oil field drilling rig which is compact in its arrangement of parts and which may be readily adapted to any type or make of drilling rig.

Another object of the invention is to provide a braking system for oil field rigs which includes a means of equalizing the action of the brake shoes when the brakes are both applied and released.

A further object of the invention is to provide a brake system wherein the brake shoes substantially enclose the brake drum to permit a maximum braking action.

Still another object of the invention is to provide a pair of brake shoes operable by a single lever and where in a single brake is used to stop the drum rotation should a failure occur in the other brake.

Another object of the invention is to provide a brake system wherein the ends of the brake bands substantially meet when encircling the brake drums and wherein the ends of said bands are pulled oppositely at substantially degrees by members of the leverage system to apply the brakes.

A further object of the invention is to provide a braking system wherein the leverage of the system progressively increases the force applied to the brake as it is moved from the normal released position to the maximum applied position.

Further objects and advantages of the invention will become apparent in the course of the following detailed description when viewed together with the accompanying drawing in which:

Fig. l is an isometric view of a braking system for oil field drilling rigs made in accordance with the teachings of the present invention.

Fig. 2 is a broken side view taken along line 2-2 of Fig. 1.

In the drawing, and particularly in the view illustrated in Fig. 1, the device is shown as consisting of a pair of brake bands spaced in operative relationship with the ends of any conventional cable drum and supplied with identical leverage mechanisms finally connected together by an equalizing bar so that when the brakes are applied, each brake band, with its set of brake shoes will contact its portion of the cable drum simultaneously with the other to provide a smooth braking action. Since the leverage arrangement for each brake band is identical, reference is made in the following description to only a single set of parts constituting one complete brake assembly.

As above mentioned, each drilling rig is provided with a driven cable drum by means of which the string of pipe is raised or lowered into the well hole, the cable having one of its ends afiixed to the drum and the other passing over a pulley in the derrick and supplied with adjustable slip jaws which grip the pipe string for lowering or raising. The drum itself is not shown in the drawing, but consists of a spool construction with the outer ends serving as brake drums which are encircled by the brake band 10 of the present invention. The brake band 10 isprovided with several brake blocks or shoes 11 held to the band in spaced relationship by means of rivets 12, or the like. The two ends of the brake band are supplied with castings 13 and 14.

The upper casting 13, atfixed to one end of the brake band 10, is provided with projecting lugs 15 having a common transverse hole 16 through the same. Into the spaces between the lugs 15, I have positioned the ends of a yoke arm 17 which is pivotally mounted to the casting 13 by means of a pivot pin 18 through the hole 16. The

yoke -17 is extended downwardly and converges into-a cylindrical end 19 which is drilled and pinned to the yoke arms 20 of a knuckle joint member 21. The knuckle joint '21 -is further-pinned to a pivot plate 22 pivotally -edly engages the'upper' end of the actuatingbar 27 and is heldin adjustedposition-by means of a lock nut 29. The

upper endof the adjusting rodZS also threadedly engages an upper yoke member -30 and is further-secured inadjustment by another lock nut Ell, as shown in Fig. 2. '-It will-be understood that the threads on the-ends of the adjusting rod are of opposite helix; so that, by turning the rod in a-given direction, 'the'diameter of the brake band it) maybe increased ordeereased to-eltect a minimum-ofslack-inthe bands whenthey are in the released position. ItWillalso be noted that the brake actuating bar 27 is extended upwardly between the lower yoke arms 1'7 and provided with a slight curvature not only 'for clearance purposes but also "to'permit the resultant forces, when .the brakes are applied, to act inopposite directions substantially 180:degrees apart. Thisis highly desirable in a braking system since the friction between the drum and brake shoes, and, therefore,-the-actual brake horse power, greatly increases as the coverage of the drumspasses O to60 percent of *the total drum surface area. 'itis apparent, therefore, that if the brake bands and shoes of the present invention are active in engaging beyond 90 percent of the drum surface area, I haveobtained maximumefiiciency from a set of brakes, andhave produced :a braking system not heretofore known orused in the prior art.

The brake actuating mechanism is more clearly illustrated in Fig. 2 wherein is-shown:a=supporting bracket 32 bolted tothevertical side wall 33 of the drum well and provided \vithupper and lower extending arms -34 and 55. The lower arm 35 is, in reality, a-yoke which carries a bell crank 36 pivotally mounted between the arms'of'the same byineans'of a-pin 37. One end of thebell crank 36 is pivotally attached to the yokemember 3tlwhichis threadedly engaged with the brake 'adjusting'rod'28. The other end of the bell crank 36 is provided with a slot 38 serving asacam surface engaged by a cam which will be subsequently described.

The upper arm 34 is bored transversely and arranged to slidably receive a brake actuating rod 39 which is'common tobcth sets of brake-mechanisms-as shown in Fig. l. Aflixed to this'rod 39 by means of a key40 'and;placed adjacent to the arm 34, 1 have 'provided lever-41 havinga depending arm 4-2 which carries a cam 43 on its lower end arranged to ride in the cam slot 38 provided in the upperend of the bell crank 36. .T he upper end of the lever 41 is made into the formof a quadrant 44 whichprojects above the top plate 45 of the rig itself. T he brake lever 46 may :be of any desired shape and bent .into 'a form suitable for actuation either by hand or the foot of the operator. The lower end=of the brake lever-46 is formed into a yoke 47 which straddles the brake rod 39 and is made to lieadjacent the quadrant 44 of the lever 41. It will be noted that the quadrant 44 is supplied with'several holes 48 by means of which the brake lever 46 may be secured in various raised or lowered positions for the convenience'of an operator.

When .the brakes are applied, that is, when the brake lever 46 is forced in :the direction of the arrow in Fig. '2, the lever "41 and, consequently, the brake actuating rod 'held to thebar by means of set screws or the like.

being allowed only "for wear in the shoes. instance, the main direction of the drum will be forward,

39 are partially rotated,-bringing the lower clevis 36 into the position as shown by the dotted lines. it will be noted here that, in the released position, the center distance between the pin 37 and the cam 43 is comparatively short. When the brakes are applied, however, this distance is increased since the lever 41 and bell crank 36 move in opposite arcuate directions. Thus the leverage is gradually increased 'from a normally released position to a maximum applied position.

Theabove description has been given to the several parts and movements of one assembly of the brake system. It isxto be understood that'the other set is made of identical parts having corresponding movements. As shown in Fig. 1, the-common brake'actuating rod 39 is extended across the upper edge of the drum well and affixed to a clevis (not shown), made similar to the lever 41 just described, but dispensing with the quadrant 44. The bands, shoes,and-'other levers are identical with those described above and are finally connected to theirown pivot-plate 22' pivotally'mounted between'the upwardly extended arms of its base casting 23. Each pivot plate 22 and 22 is made substantially in the form of a triangle asshown in the drawing,=with the inner corners arranged for pivotal attachment'toa pairof yoke members 49 and 49. The inner ends of a common stabilizing bar 50 which with a transverse-bore slidably receiving the stabilizing bar '50. Mounted upon the stabilizing bar 50, upon each side of the stop "52, Ihave provided sleeves 53 and 54 Encircling the bar 50, between the sleeves and the central stop 52, I have provided compression springs 55 and 56 whichmaybe set to any amount of compression by moving and setting the sleeves.

-It is nowapparent'that any movement-of either of the pivot plates 22 or 22, in an effort to rotate about its mounting pin, will cause-a corresponding movement to the other plate. If no force is exerted on either plate, then both plates will assume a neutral, balanced position due to the act-ion of'the compression springs 55 and 56. 'Such a construction is highly advantageous when applied to a braking system in that'the brakes are appliedsmoothly and evenly to the brake drums.

Each of the base'castings'23 and 23' are supplied with a stop "member57 which, in reality is-a web connecting the side erms of eachbase casting at "the outer ends thereof, and serving as a-stop member to limit the rotation of the pivot plates in either direction of rotation about their mounting pins. Thus, should failure occur in either set of brakes, such as by a sheared pivotpin, that particular pivot 'plate will be thrown against its'stop 57 to prevent further damage and'to hold the oppositepivot plate'while the brakes are applied.

The device is simple in construction and lends itself readily to any typedrilling'ring. While the component parts of the system are sufiiciently strong for the purpose intended, they may be compactly arranged within a drum well and occupy a minimum of space. The stabilizing bar insures an even, simultaneous pressure applied to the brake drums and asimultaneous release of the shoes. The working height of the actuating brake lever 46 may be quickly and easily adjusted to suit the operator and the brakes may be settoan initial tightness by means of the brake adjusting rods 28.

The fact that the brake shoes cover approximately percent of the braking surface of the drums cannot be overemphasized. As before mentioned,the end castings l3 and 14 substantially meet at the band ends, thespace left In the present that is,ina direction of rotation anti-clockwise inthe view 75 =illustrated in Fig. '1. Thusth'e greater thrust will be against the bottom yokes 17 and against the base castings 23 and 23. Since the two sets of brakes are equalized by means of the equalizing bar 50, they are made to engage simultaneously. Should the original brake setting be such that one brake engages the drum before the other, the action of the stabilizing bar will equalize any subsequent pressure applied by a rotation of the pivot plates 22 and 22'.

It is to be understood that the above illustration has been by way of example only and that changes could be made in the actual construction without departing from the scope of the invention as defined by the following claims.

I claim:

1. Apparatus of the class described comprising, a plurality of brake drums, brake bands extending respectively around said brake drums, lugs fixed respectively to the ends of said brake bands, yokes connected respectively to a lug on one end of each of said brake hands, a plurality of stationary base members, pivot plates pivotally mounted respectively in each of said base members and connected to said yokes, a stabilizing bar connected between said pivot plates, a stationary stop member provided with a bore slideably receiving said bar, sleeves adjustably fixed to said bar on opposite sides of said stop member, compression Springs held respectively between each of said sleeves and said stop member, a rotatably mounted brake actuating rod, tension transmitting means extending substantially tangential to said brake bands respectively through said yokes and connecting the lugs on the other end of said brake bands to said br-ake actuating rod, and means for rotating said brake actuating rod.

2. Apparatus of the class described comprising a plurality of brake drums, brake bands extending respectively around said brake drums, lugs fixed respectively to the ends of said brake bands, yokes connected respectively to a lug on one end of each of said brake bands, a plurality of stationary base members, pivot plates pivotally mounted respectively in each of said base members, knuckle joints respectively connecting said pivot plates to said yokes, a stabilizing bar connected between said pivot plates; a stationary stop member provided with a bore slidably receiving said bar, sleeves adjustably fixed to said bar on opposite sides of said stop member, compression springs held respectively between each of said sleeves and said stop member, a rotatably mounted brake actuating rod, tension transmitting means extending substantially tangential to said brake bands respectively through said yokes and connecting the lugs on the other end of said brake bands to said brake actuating rod, and means for rotating said brake actuating rod.

3. Apparatus of the class described comprising, a plur-ality of brake drums, brake bands extending respectively around said brake drums, lugs fixed respectively to the ends of said brake bands, yokes connected respectively to a lug on one end of each of said brake hands, a plurality of stationary base members, pivot plates pivotally mounted respectively in each of said base members, knuckle joints respectively connecting said pivot plates to said yokes, a stabilizing bar connected between said pivot plates, a stationary stop member provided with a bore slideably receiving said bar, sleeves adjustably fixed to said bar on opposite sides of said stop member, compression springs held respectively between each of said s-leeves'and said stop member, a plurality of brake adjusting"rods,

tension transmitting means extending substantially tangential to said brake bands respectively through said yokes and connecting the lugs on the other end of said brake bands to said brake adjusting rods, a rotatably mounted brake actuating rod connected to said brake adjusting rods, and means for rotating said brake actuating rod.

4. Apparatus of the class described comprising, a plurality of brake drums, brake bands extending respectively around said brake drums, lugs fixed respectively to the ends of said brake bands, yokes connected respectively'to a lug on one end of each of said brake bands, a plurality of stationary base members, pivot plates pivotally mounted respectively in each of said base members, knuckle joints respectively connecting said pivot plates to said yokes, a stabilizing bar connected between said pivot plates, a stationary stop member provided with a bore slideably receiving said bar, sleeves adjustably fixed to said bar on opposite sides of said stop member, compression springs held respectively between each of said sleeves and said stop member, a plurality of brake adjusting rods, means extending respectively through said yokes and connecting the lugs on the other end of said brake bands to said brake adjusting rods, pivotally mounted bell cranks attached respectively to said brake adjusting rods, said bell cranks being provided with slots forming cam surfaces, a rotatably mounted brake actuating rod, levers mounted upon said brake actuating rod, said levers carrying pins arranged respectively for camming action against said cam surfaces, and means for rotating said brake actuating rod.

5. Apparatus of the class describged comprising, a brake drum, a brake band extending substantially around said brake drum, lugs fixed respectively to the ends of said brake band, a yoke connected to a lug on one end of said brake band, a stationary base member, means connecting aid base member to said yoke, a pivotally mounted bell crank, means extending through said yoke and connecting a lug on the other end of said brake band to said bell crank, said bell crank being provided with a slot forming a cam surface, a rotatably mounted brake actuating rod, a lever mounted upon said brake actuating rod, said lever carrying a pin arranged for camming action against said cam surface, and means for rotating said brake actuating rod.

6. Apparatus of the class described comprising, a brake drum, a brake band extending substantially around said brake drum, lugs fixed respectively to the ends of said brake band, a yoke connected to a lug on one end of said brake band, a stationary base member, means connecting said base member to said yoke, a brake adjusting rod, means extending through said yoke and connecting a lug on the other end of said brake band to said brake adjusting rod, a pivotally mounted bell crank attached to said brake adjusting rod, said bell crank being provided with a slot forming a cam surface, a rotatably mounted brake actuating rod, a lever mounted upon said brake actuating rod, said lever carrying a pin arranged for camming action against said cam surface, and means for rotating said brake actuating rod.

7. A apparatus of the class described comprising, a brake drum, a brake band extending substantially around said brake drum, lugs fixed respectively to the ends of said brake band, a yoke connected to a lug on one end of said brake band, a stationary base member, a pivot plate pivotally mounted in said base member, means connecting said pivot plate to said yoke, a brake adjusting rod, means extending through said yoke and connecting a lug on the other end of said brake band to said brake adjusting rod, a pivotally mounted bell crank attached to said brake adjusting rod, said bell crank being provided with a slot forming a cam surface, a rotatably mounted brake actuating rod, a lever mounted upon said brake actuating rod, said lever carrying a pin arranged for camming action against said cam surface, and means for rotating said brake actuating rod.

References Cited in the file of this patent UNITED STATES PATENTS 731,940 Osgood June 23, 1903 1,440,842 Smith Jan. 2, 1923 1,956,433 Young Apr. 24, 1934 1,997,727 Greve Apr. 16, 1935 2,116,013 Carson et a1. May 3, 1938 2,271,247 Brown Jan. 27, 1942 2,414,677 Tremolada Jan. 21, 1947 

